In general, the refrigerator repeats a refrigerating cycle in which refrigerant is compressed-condensed-expanded-evaporated, for cooling down an inside thereof for fresh storage of food, and the like.
For forming the refrigerating cycle of the refrigerant, the refrigerator is provided with a compressor, a condenser, an expansion valve, and an evaporator. The compressor boosts gaseous refrigerant from low temperature/pressure to high temperature/pressure, and the condenser receives the refrigerant from the compressor, and makes the refrigerant to heat exchange with external air, to condense the refrigerant. The expansion valve has a diameter smaller than other portion, for dropping a pressure of the refrigerant from the condenser. The evaporator absorbs heat from the refrigerator as the refrigerant passed through the expansion valve is evaporated at a low pressure.
The structure, and operation of a related art refrigerator will be described with reference to the attached drawings. FIG. 1 illustrates a longitudinal section of a related art refrigerator schematically, and FIG. 2 illustrates a longitudinal section of a defrosting process of an evaporator in a related art refrigerator.
Referring to FIG. 1, an inside of a refrigerant case 100 is partitioned into a freezing chamber 110 and a refrigerating chamber 111 with a barrier 101. Though the freezing chamber and the refrigerating chamber can be partitioned in up/down direction as shown, the freezing chamber and the refrigerating chamber can be partitioned in left/right direction. In the meantime, the barrier 101 has at least one communication hole 101a for free flow of cold air between the freezing chamber and the refrigerating chamber.
In general, the freezing chamber 110 has cold air heat exchanged at the evaporator 200, and introduced thereto, to maintain a temperature thereof at about −18° C., and the refrigerating chamber 111 has the cold air passed through the freezing chamber 110, to maintain a temperature thereof at about 0-7° C.
Behind the freezing chamber 110, there is a cold air duct 500 for receiving the air passed through the freezing chamber and refrigerating chamber for heat exchange. For this, the cold air duct 500 has a cold air outlet 510 and a cold air inlet 520 in an upper portion and a lower portion, respectively.
Inside of the cold air duct 500, there are an evaporator 200, a fan 400, and a motor 410. The motor 410 drives the fan, and the fan 400 forcibly circulates the cold air cooled down as the air passes through the evaporator 200 through the freezing chamber 110. Under the duct 500, there is a machine room 120, provided with the compressor and the condenser of the refrigerating cycle, and a heat dissipation fan for forcibly blowing air to cool down heat generated at the condenser.
In the meantime, the operation of the refrigerator will be described.
Upon tuning on power in a state the freezing chamber 110, and the refrigerating chamber 111 is filled with food, the compressor in the machinery room is operated in response to a control signal from a controller (not shown), and the evaporator 200 makes heat exchange with air inside of the refrigerator according to the refrigerating cycle. According to this, the air is discharged to the freezing chamber 110 by the fan 400 after the air is cooled down as the air heat exchanges with the refrigerant passing through the evaporator 200, and a portion of the cooled air is introduced into the refrigerating chamber 111 through the communication hole 101a Thereafter, the cold air heated as the air circulates through the freezing chamber 110 and the refrigerating chamber 111 is introduced into the duct 500 through the cold air inlet 520.
In the meantime, moisture in the cold air forms frost on the evaporator 200 during operation. While a surface of the evaporator 200 has a low temperature, an environmental temperature is relatively high, dew is formed on the surface of the evaporator, which is frozen on the surface of the evaporator 200, to form the frost.
Since the frost impedes flow of the cold air, leading cooling efficiency poor, defrosting operation is required for removing the frost in regular time intervals. For this, there are a plurality of defrosting heaters 300 around the evaporator 200.
In the defrosting heater 300, there are contact defrosting heaters (not shown) in contact with the evaporator 200 for transmission of heat to fins on the evaporators 200, and non-contact defrosting heater 300 spaced from a predetermined distance from the evaporator 200 for transmission of heat to the fins on the evaporator by radiation. Depending on refrigerators, either, or both defrosting heaters are applied.
In the defrosting operation, by applying power to the defrosting heater 300 for a predetermined time period to transmit heat to the fins on the evaporator 200, the frost can be melted down, and remove the frost, from the evaporator 200. Water from the frost is drained through a drainpipe to an outside of the refrigerator, or evaporated for itself.
In the meantime, because of temperature rise due to heat from the defrosting heater 300, there is a high cooling load at an initial operation of the next refrigerating cycle, to put a great burden on the evaporator 200, leading a cooling efficiency poor, at the end.
Moreover, since the defrosting heater 300 receives power to generate heat, excessive power is required for elevating a temperature to a required level, that increases power consumption.